[core] Fix stack buffer reference after it goes out of scope (#3034).

srtcore/channel.cpp

@@ -864,6 +864,10 @@ srt::EReadStatus srt::CChannel::recvfrom(sockaddr_any& w_addr, CPacket& w_packet
 #ifndef _WIN32
     msghdr mh; // will not be used on failure
 
+#ifdef SRT_ENABLE_PKTINFO
+   // This buffer is mounted inside mh so it must stay in the same scope
+   char mh_crtl_buf[sizeof(CMSGNodeIPv4) + sizeof(CMSGNodeIPv6)];
+#endif
     if (select_ret > 0)
     {
         mh.msg_name       = (w_addr.get());
@@ -878,7 +882,6 @@ srt::EReadStatus srt::CChannel::recvfrom(sockaddr_any& w_addr, CPacket& w_packet
 #ifdef SRT_ENABLE_PKTINFO
         // Without m_bBindMasked, we don't need ancillary data - the source
         // address will always be the bound address.
-        char mh_crtl_buf[sizeof(CMSGNodeIPv4) + sizeof(CMSGNodeIPv6)];
         if (m_bBindMasked)
         {
             // Extract the destination IP address from the ancillary